For production of electronic elements, such as memory chips, microprocessors, application specific integrated circuits or logic components, very precise and reliable working semiconductor production devices are required. The product to be manufactured, in many cases a semiconductor component, that is required to operate reliably and shall comprise reproducible electrical and physical properties. Several hundred single process steps need to be carried out for manufacturing such a semiconductor component. At the same time, the trend towards smaller and smaller structures, in other words, the ever increasing amount of semiconductor components per square centimeter always provides new challenges to manufacturers of semiconductor manufacturing devices. The production of error free or flawless isolation layers at low temperatures is an urgent problem in order to be able to produce semiconductor components comprising semiconductor structures of 45 nm, 32 nm, and even smaller, which are as reliable as logic components having a logical semiconductor structure of 65 nm. In the car industry, it is, e.g., requested that the electronic components used in that area are able to function over a long period without errors since human lives may depend from the reliable operation thereof. In order to fulfil such requirement, the reliability of the components needs to be improved accordingly, wherein inter alia a substantial approach exists in producing flawless dielectric layers or in producing layers that may be changed to a flawless condition via a corresponding post treatment.
Another requirement for the present semiconductor technology consists of lowering the thermal budget or heat input during production of, e.g., thermal oxide layers or other dielectric layers, as mentioned above.
Furthermore, new requirements in the development of transistors need to be fulfilled e.g. with respect to so called “metal-gates”. Selective oxidation of silicon to the materials tungsten, tungsten silicide, tantalum nitride, titanium nitride, etc., should be carried out at low temperatures.
A still further request is a uniform oxidation of semiconductor structures consisting of differently doped silicon and the oxidation of silicon nitride. Furthermore, the production of reliably operating semiconductor component requires a production of flawless layers having high dielectric constants on tantalum, niobium, tantalum nitride, niobium nitride, and similar materials, e.g., as well as the post-treatment of flawed layers that were deposited via CVD and ALD processes, respectively.
In the past, dielectric layers were produced via thermal oxidation in ovens or in RTP reactors and via CVD processes or recently, via ALD processes wherein these processes generally do not produce flawless layers with respect to the electrical properties thereof, owing to the respective production method. Thus, contamination or flaws in the crystal structure may lead to electrically flawed layers during thermal oxidation. Problems with nucleation, as well as inclusion of particles, are the cause of electrically weak points of CVD and ALD layers, especially of thin layers, as well as inclusions of particles.
A further drawback of thermal oxidation is the so called thermal budget, i.e., the product of the process temperature multiplied with the process time. In many processes of semiconductor production, such as thermal oxidation and nitration, the thermal budget for the required layer building is so high that significant defects or other undesirable changes of the semiconductor element may be caused during the layer build up. For example, the diffusion profiles of the doping agents may be disturbed when the temperature budget gets too high, which decreases the reliability of the components or impacts performance.
Another drawback of thermal oxidation exists in differently doped and differently crystalline oriented silicon being oxidized with different velocities, which may lead, e.g., to different breakthrough voltages of the oxide depending on the orientation of the crystal. This poses a substantial problem in semiconductor production.
Another drawback of the thermal oxidation exists in the fact that silicon nitride oxidizes only minimally during oxidation of silicon. With currently used semiconductor components, structures are present in which a silicon nitride is located directly adjacent the silicon surface. With such structures, thermal oxidation processes may be used only limitedly or may not be used at all. With such oxidation processes, either no oxide layer or no desired oxide layer is formed in the transition area between the silicon surface and the silicon nitride layer.
Methods are known which try to avoid such drawbacks. EP 1,018,150 describes a method for forming an oxide, wherein a substrate is heated to a temperature which is sufficiently high to initiate a reaction between an oxide containing a gas and a hydrogen gas near the substrate in a process chamber. In this known method, hydrogen and oxygen are directed out a heated silicon disc which is at a raised temperature of higher than approximately 850° Celsius at a pressure of approximately 1/100 atmospheric pressure, and a thin oxide layer of silicon and silicon nitride is formed. This kind of oxidation, in the literature also known under the name of In-situ wet oxidation, only produces thin oxide layers and furthermore, needs high temperatures which are unacceptable in many cases.
A selective oxidation of silicon to metals at room temperature or at a temperature of a few hundred degrees Celsius is not possible with such a method.
Layers having a high dielectric constant, especially crystalline layers, cannot be deposited flawlessly on large areas.
At the moment, there are devices in which it is tried to implement an oxidation of silicon on the base of RF excitation of a plasma. U.S. Pat. No. 7,214,628, e.g. discloses a method for gate oxidation wherein a device is used, in which an inductively formed plasma is generated via pulsed microwave radiation. In this method, the plasma is purposely held at a sufficiently large distance to the substrate in order to avoid ion generated defects when forming an oxide layer. The plasma is switched on and off. During the off interval, ions from the plasma may reach the substrate. During formation of the oxide layer, chamber pressure and pulse cycle are limited such that the defects induced via ion bombarding in the oxide layer are kept as small as possible. However, the plasma used in this facility does not achieve the density of the low energy ions and electrons, which are required in order to obtain the desired effects, i.e., in order to form a layer having a substantial thickness on the substrate within short time.
The US 2007/0221294 A1 also describes a plasma generating device on a microwave basis for forming an oxide or nitride film. In this device, a microwave plasma is directed through a distributor plate, which is spaced from a substrate to be processed, onto said substrate in order to form homogeneous oxide and nitride layers, respectively. Also, this microwave plasma does not comprise the necessary plasma density for achieving the desired effects due to the way of feeding into the process chamber.